Dental restorations containing oxide ceramics are known since a couple of years. Especially zirconia has been used for manufacturing dental ceramic support structures.
For the production or colouring of aesthetic dental restorations based on oxide ceramics different processes have been suggested.
WO 2004/110959 (corresponding to US 2006/117989 A1) relates to a colouring solution for ceramic framework. The solution comprises a solvent, a metal salt and polyethylene glycol having a molecular weight in the range of 1.000 to 200.000.
WO 00/46168 A1 (corresponding to refers to colouring ceramics by way of ionic or complex-containing solutions containing defined concentrations of at least one salts or complexes of the rare earth elements or of the elements of the subgroups. The solution might contain additives like stabilizers, complex builders, pigments and beating additives.
Similar approaches are described in US 2010/0221683 A1 (Franke), US 2007/0062410 A1 (Thiel) and U.S. Pat. No. 6,709,694.
US 2010/221683 describes a colouring solution for colouring a dental ceramic article, wherein the solution comprises a solvent and a colouring agent comprising rare earth element metals or ions and transition metals or ions. The dental ceramic article may comprise ZrO2 and/or Al2O3.
U.S. Pat. No. 6,713,421 relates to blanks comprising zirconium oxide-based ceramic with an addition of 0.1 to 0.50 wt % of at least one of the oxides of the elements aluminium, gallium, germanium, indium and their use.
US 2007/0292597 A1 (Ritzberger) describes a process for the preparation of blanks and dental shaped parts which contain colouring compounds, wherein the process comprises the steps of a) coating an oxide powder with a colouring substance to produce a coloured powder, b) pressing the coloured powder to produce a shaped body and c) sintering the compressed body.
CN 101870582 (The 9th People's Hospitoal) describes a preparation method for tooth coloured dental ceramics based on Y-TZP powder using the rare earth metal oxides Pr611, CeO2, Er2O3 and MnO2.
U.S. Pat. No. 5,219,805 relates to an ivory-colored zirconia sintered body which contains as a main component stabilizer-containing ZrO2 and based on the stabilizer-containing ZrO2 certain amounts of Er2O3, Pr6O11, Fe2O3 and ZnO.
WO 01/12097 (corresponding to AU 200072766) relates to a process for the preparation of dentures comprising the steps of a) preparation of a blank, b) processing the blank by milling methods, c) dense sintering the blank in a certain temperature range, wherein the blank comprises a pre-sintered material having a certain raw-breaking resistance. The pre-sintered blank may comprise a zirconium oxide or aluminium oxide ceramic.
However, there is still room for improvement especially with regard to the requirements to be fulfilled with respect to modern dental materials. Many of the commercially available dental restorations still do not show the appearance of natural dental teeth.
Thus, it is generally an object of the invention to provide a dental article which can be used for making aesthetic dental restorations.